Chestnut bridle leather briefcase with white wax bloom on the flap and one corner buffed clean.
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Wax Bloom: Buff It Off or Leave It

ByPeter Joeseph 'Briefcase Maker' Kalafatis

Do not scrub it. Do not wash it. Do not reach for saddle soap.

Wax bloom is a white haze that rises on English bridle leather when the waxes and fats packed into it at the tannery work their way back out, and when you find it on a briefcase you just pulled out of a closet after a dry winter, the first thing to do is nothing at all. Do not scrub it with a wet rag. Do not hit it with a household cleaner, and leave the saddle soap, the vinegar and the alcohol wipe where they are. Set the case on a table, keep your hands in your pockets for a minute, and find out what you are looking at, because the haze on bridle is usually the leather telling you what it is made of, and once in a while it is something else that needs a very different answer.

Video: What does wax bloom look like on an authentic English bridle leather briefcase?, from Marcellino NY Briefcase Maker on YouTube.

Hands off first

The worst thing that happens to a bloomed case is often the owner’s first reaction.

Macro view of frost-like white wax bloom on the surface of bridle leather.

The reason to hold off is simple. Bloom sits on the surface and does no harm, while the things people grab in a hurry to get rid of it can do plenty.

Saddle soap is the classic mistake. The Canadian Conservation Institute’s care note for vegetable-tanned leather calls it “very alkaline, which causes degradation of the leather,” and says care of stiff leathers should not include saddle soap or a dressing. That note is written for museum objects, not briefcases in daily use. The chemistry does not check which one it is working on.

My Leather Care page says the plain version for a working bag. Cleaners take dirt out, and “They also take out oil and make it dry.” Bloom is oil and wax that has come to the top. Wash it off with soap and you strip the very grease the tannery packed in, then leave the surface underneath thirstier than it was before the haze showed up.

Water comes next. The same page warns that “No leather conditioner is waterproof,” and that water left sitting can go in and leave spots. Scrub a wet rag across a bloomed panel and you trade a haze that buffs off in a minute for a water mark that fades on its own schedule, not yours.

So, hands off. Then look.

What the white is made of

Bridle leather is stuffed at the tannery, and stuffing can come back out.

English bridle is made heavy on purpose. On my Leather Choices page I call it a finish that is “traditionally very waxy, thick, heavy, and stiff.” The Japanese bag maker Tsuchiya Kaban, describing the bridle it uses, says the hides are double-tanned and drum-tumbled before “generous amounts of wax” go on by hand in several layers. It lists the result, a frost-like white bloom, among the leather’s identifying marks.

Conservators have a name for the same deposit. The AIC-affiliated conservation wiki entry on spew defines it as a substance deposited on the leather’s surface, usually waxy and white or brown, formed when fats and oils reach the surface and harden in the air. Ellen Carrlee, a conservator writing in Alaska State Museums Bulletin 58, describes fatty spew as a “white bloom or haze on the surface of the leather” and cites an analysis that found one sample to be a mixture of palmitic and stearic acids, saturated fatty acids from the breakdown of animal oils. Any line cook knows the look. It is the fat that sets white on top of a pot of stock left overnight in the walk-in.

What brings it up is the weather. My own page puts it this way: in certain climates and drier environments, the waxes “‘bloom’ to the surface in a haze.” The MSPC team, in a journal post on bloom, ties it to falling temperatures, when heavily greased leather’s oils solidify and rise. The archive stories agree. The Folger Shakespeare Library found a white deposit on bindings in a vault whose temperature had recently been lowered, and the special collections team at Miami University traced theirs to a winter drop after an environmental control failure.

A closet, a car trunk, a cold office over the holidays. Same physics, smaller room.

Bloom or mould: the tests that settle it

One melts under a little heat, and the other grows.

Hand buffing wax bloom off a bridle leather briefcase with a cloth and conditioner.

Here is where hands off pays for itself. My opinion: an owner who is slow here is never sorry. Bloom and mould can both look like white dust, and the Canadian Conservation Institute’s own note on removing mould from leather admits that oils and waxes can leave a white deposit “that could be misinterpreted as mould.”

Start with the conditions. That CCI mould note says mould grows at relative humidity from 65 to 100 percent, with warmth and poor air circulation, and gives rough timings: about two days at 90 to 100 percent, ten days at 80, a hundred days at 70. Carrlee’s bulletin puts its comfort zone above 70 percent and 70°F. So a case kept in a dry, heated house over winter points to bloom. One left in a damp basement, or sealed in a plastic bag where the air never moves, points the other way.

Then the feel. CCI’s vegetable-tanned leather note describes fatty blooms as “slightly waxy in texture.” Bloom feels like the wax it is, slick under a fingertip rather than powdery.

Then heat. Both library posts used it. The Folger staff heated a sample, and the deposit melted under low heat, which is how they knew it was spew and not mould. A leather-care dictionary published by a care-products firm gives the same test with a hair dryer: fatty spue melts and disappears for a while, mould stays put.

CCI also gives a solvent test: dampen a swab with mineral spirits and rub an inconspicuous spot. If the white goes, it was likely wax. And CCI’s rule for doubt is the one to follow: if you are not sure, treat it as mould.

That rule earns its keep, because mould gets a different response entirely. The CCI note calls for at least an N95 or N100 respirator, disposable gloves and non-vented goggles even for a small patch, HEPA vacuuming rather than wiping, and no cleaning while the leather is still damp, since mould smears instead of lifting. People with allergies, breathing problems or weak immune systems should stay away from it. A mouldy bag is a job for someone set up to handle it. Not a job for a buffing cloth.

The trade wants it and the owner does not

Two true things about the same white haze.

Here my own pages pull in two directions, and I wrote both of them. On the Leather Choices page I call bloom a highly prized effect, one that “authenticates true English style bridle leather.” In the next breath the page says, “You buff it out with a cloth and oil conditioner.” Prize it, then wipe it off. Both sentences are mine, and I am not taking either one back.

To the trade, bloom is a fingerprint. It shows up because the leather was stuffed the old way, with more wax and fat than a lighter finish carries. Tsuchiya Kaban lists it as a trait of the leather. The MSPC post says outright: “Even if bloom appears, there is no need for any special treatment.” The library people at Miami say spue is unsightly but “not, generally speaking, harmful.”

Carry that case into a meeting, though, and the fingerprint stops counting. Nobody across a table reads a white film on a chestnut briefcase as proof of tannery practice. They read it as dust, and they read the man holding it as somebody who does not own a cloth.

My opinion: the bloom is the tannery’s signature, not the owner’s problem. I can respect what it proves and still tell you to wipe it off. Knowing why it is there is the reason not to panic, not a reason to leave it.

Except I have said the opposite, too. On a new hide, I have told people the tannery’s own tallow coat is fine to leave on, and that it shows as a light haze. So the same man who says wipe it says leave it. The leather did not change between those two sentences. The room it was going into did.

There is also a difference between the bloom on a new hide and a haze that keeps coming back on an old bag. Imported UK bridle, which the Leather Choices page lists among the leathers used here, carries a light greasy top coat from the tannery, as the Leather Care page explains, and American bridle does not. My opinion, having cut both: English bridle holds so much wax that it stays glossy and takes years to break in, while American bridle fades and patinas within months. The heavier the stuffing, the more there is to come back up. A bloom that returns year after year on a case that gets conditioned heavily may be the conditioner itself coming back up, which the Miami post calls secondary bloom from earlier dressings. That one is telling you to go easier with the tin.

Buffing it out

A clean cloth, a little conditioner and a few minutes.

Workshop bench with a bridle leather briefcase, horsehair brush and cloths for removing wax bloom.

Once you know it is bloom, the method on my page is short, and I stand by it: buff it with a cloth and oil conditioner. The Leather Care page gives the conditioning routine in general: conditioner on a clean cloth, rubbed briskly into the leather, left to sit, then the excess buffed off with a clean dry cloth. Light color transfer can show up on the cloth at first, which the same page also warns about.

What goes on the cloth, for me, is beef tallow or a leather oil. Tallow I warm first. On finished vegetable-tanned pieces it goes in by hand, slowly, with the heel of the palm doing most of the work while the fingers only steer, until the haze goes and the brown comes back up from underneath, which is the whole show.

Other people do it with less. Barbara Adams Hebard, a conservator at Boston College, describes on the AIC community forum gently brushing bloom off book bindings with a soft brush. The MSPC team suggests a horsehair brush with light pressure, then a soft dry cloth, or gentle warmth from a hair dryer or a warm room so the solid oils melt back in. The leather-dictionary firm uses a hair dryer as well. If you use heat, keep it low and brief and keep it moving. Bridle is full of wax, and wax that gets hot enough to run will darken the leather unevenly. That is my opinion, not a source’s.

Prevention is mostly storage. CCI recommends a stable relative humidity of 45 to 55 percent and 18 to 20°C for museum leather; in my view that band suits a case in a closet just as well. Keep it out of plastic bags, which Andar’s guide to white marks on leather warns can trap moisture and invite mould, and away from radiators, since the whole point of conditioning is to keep the leather from drying out. Even then, a dry snap or a cold room may bring it up again.

My channel has a video on what wax bloom looks like on an authentic English bridle briefcase, and it is the one at the top of this page. For how this leather changes over decades of use, the post on how a Marcellino briefcase will look in 100 years picks up the story, and The Art of Vegetable Tanning covers how the leather gets its tannins in the first place.

The bloom will come back. It came from inside the hide, and there is more where that came from.

Skidmore’s Leather Cream: A leather conditioner cream, one option for the conditioner step. See it on Amazon (affiliate link).

As an Amazon Associate I earn from qualifying purchases. A commission may be earned if you buy through this link, at no extra cost to you.

Sources

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